It is common practice to measure the pressure over a filter or a semi-permeable diaphragm in liquid handling systems, in order to monitor for clogging, disruption or other types of filter failure. It is also common practice to use pressure sensors to measure the pressure difference over an osmotic diaphragm (osmotic pressure). Pressure sensing is also used to monitor for clogging, disruption or other types of filter failure in gas handling systems.
Such measurements can be performed by using a differential pressure sensor with ports to each side of the diaphragm or with two absolute pressure sensors, each of them with inlet ports from each side of the diaphragm to be monitored.
Pressure measurement in the above known systems is typically done by separate sensors, which in the case of liquid media are costly and include bulky transducers with stainless steel fronts. The pressure over the diaphragm is calculated by measuring the line-pressure on each side of the diaphragm or by building a differential pressure sensor with pressure inlets to the liquid volumes on each side of the diaphragm. Such differential pressure sensors are particularly demanding and costly to make.
In small liquid systems such as micro-fluidic devices or lab-on-chip solutions and small gas handling systems, separate pressure sensors in the form of packaged devices take up a large volume of space and are often therefore ineffective or impossible to use.
Very thin diaphragms require support structures. In order to build a thin diaphragm that covers a relatively large area it is common practice to build the complete diaphragm as a matrix of many relatively small diaphragms supported by an array or matrix of support beams, in order to make the total structure strong enough to withstand a pressure induced over the diaphragm.